1. Field of the Invention
This invention relates to steam boiler low-water cutoff systems, which prevent the activation of the boiler's heating elements in unsafe conditions. Particularly this invention relates to a method and apparatus for flushing steam boiler low-water cutoff systems. More particularly this invention relates to in-service flushing of solid particles, scale and debris from the working components of steam boiler low-water cutoff systems. Even more particularly this invention relates to the rerouting of a water make-up line through a flushing unit attached to a steam boiler low-water cutoff system that allows for in-service flushing of solid particles, scale and debris from the working components of the steam boiler low-water cutoff system each time make-up water is added to the steam boiler system.
2. Description of the Related Art
Most steam or hot water boiler heating systems are comprised of a water reservoir, a firing mechanism and means to add water to the system. The firing mechanism, usually a coal, oil or gas burner, heats the water in the water reservoir to produce steam or hot water for heating residential, commercial or industrial buildings. Heating system burners are normally controlled by a solenoid actuated valve, which controls the supply of air to coal fired burners or which controls the flow of fuel to oil or gas type burners.
Over time, as the hot water or steam circulates through the heating system, small amounts of water or steam are lost to the surroundings. Additional water must be added to the heating system to make up for this lost water. This water is replenished into the heating system through a make-up water line. If, however, the water is not properly replenished and the water level in the boiler falls below a safe operating level while the burner continues to operate, serious damage or destruction of the heating system may occur. Therefore, in addition to the heating system components listed above, safety codes require that control devices be installed for disabling the burner when the water level in the heating system falls below a predetermined hazard level. These control devices are known in the art as low-water cutoff systems.
Many low-water cutoff systems are comprised of a sight gauge and an electrical or mechanical float-type water level sensor. The water level sensor monitors the boiler water level. Typically, when the water level sensor detects an inadequate water level for operation it triggers a control switch that adds water to the boiler while simultaneously deactivating the burner until the water level is brought back up to a sufficient level. The sight gauge allows an operator to visually monitor the water level in the heating system and may contain additional means for deactivating the boiler in unsafe conditions.
Typical displacement or float-type water level sensors are attached to a pivotal linkage on the interior of a sensor chamber and are surrounded by a protective sleeve or bellows. The sensor chamber holds an amount of water, which in optimum conditions mirrors the level of water in the boiler. As the water level in the boiler falls so will the water level in the sensor chamber. As the water level in the sensor chamber falls the buoyant force on the float is reduced which causes the float to drop. If the float dips below a certain predetermined level it triggers a cutoff signal, usually a solenoid actuated valve, that will prevent the burner from operating. The float will also trigger a separate valve connected to the water make-up line that will supply additional water to the boiler. One popular example of the mechanical float-type low-water cutoff system is the McDonald Miller No. 67.
Other low-water cutoff systems employ electrical sensors that work in much the same way as the float-type sensors. An electrical sensor is placed on the inside of a water filled sensor chamber below the low water line. The sensor is connected to an electrical circuit such that while the sensor is submerged in water it completes the circuit. As the water in the boiler drops, which causes the water to drop in the sensor chamber, the electric sensor will become exposed, thereby breaking the circuit and triggering a set of switches that deactivates the burner and activates the water feed cycle.
Unfortunately, regardless of the type of sensor used, after extended periods of time many of these types of low-water cutoff systems become defective due to a buildup of rust, scale or debris on the working parts of the sensor. As debris collects in and around the working components of a sensor, it becomes obstructed and, therefore, ineffective at detecting the true boiler water level. If a sensor fails to detect the proper level of water in the boiler the burner will continue to fire, leading to permanent damage of the heating system.
Depending upon the climate, these heating systems may remain dormant throughout the summer, as many households and businesses do not require heat during these months. This dormant period allows sediment and debris to collect that might obstruct or hinder the performance of the float system. To prevent and remove the buildup of rust, scale and debris, most low-water cutoff systems provide a manual flush valve, which allows for manual periodic flushing of the water surrounding the working components of the low-water cutoff system. Most manufacturers will recommend maintenance schedules that require periodic inspection, flushing and testing of these safety control systems. Unfortunately many homeowners, absentee landlords or businesses without full time maintenance personnel rarely perform this much-needed flushing function, causing many hot water boiler heating systems to get ignored until problems arise.
Many recent improvements in the field, for preventing the low-water firing problem, concentrate on the design of special sensing devices. For example, U.S. Pat. No. 5,060,560 (1991, L. VanDeMark) teaches the use of a backup safety probe or sensor that uses relays to interrupt the flow of electrical energy to the heating element. The backup sensor unit is located outside of the main pressure vessel, in a conduit in fluid communication therewith. This device reduces the risk of overheating by the burner, however, it requires an operator skilled in the maintenance of heating systems to manually blow-down the debris from the low-water cutoff system prior to restarting the heating system. This may result in unnecessary extended periods of dormancy of the heating system when it is most needed.
U.S. Pat. No. 5,224,445 (1993, L. Gilbert) teaches the use of an electronic sensor, which deactivates the burner in low-water or dry conditions and prevents reactivation of the burner until the boiler has returned to a safe condition. This device also reduces the risk of damage to the system caused by overheating but also would require manual blow-down of any debris and resetting of the low-water cutoff system prior to the restart of the heating system.
U.S. Pat. No. 4,941,435 (1990, T. Person) teaches the use of an electronically activated blow-down valve. This system utilizes a microprocessor, which signals a solenoid valve, to open or blow-down for a period of between one and twenty seconds, whenever the water feed cycle to the boiler commences. One drawback with this system is that it requires the use of multiple components including a microprocessor, which increases the chance of system failure. Another disadvantage with this system is that it requires an appropriate environment into which rusty or other debris-laden water may be randomly discharged from the heating system.
What is needed is a method and apparatus for in-service flushing of solid particles, scale and debris from the working components of steam boiler low-water cutoff systems.
What is further needed is a method and apparatus for in-service flushing of solid particles, scale and debris from the working components of steam boiler low-water cutoff systems that can be added to newly manufactured low-water cutoff systems.
What is further needed is a method and apparatus for in-service flushing of solid particles, scale and debris from the working components of steam boiler low-water cutoff systems that can be easily annexed to a variety of currently installed low-water cutoff systems, including both electronic and mechanical type sensor systems.
What is further needed is a method and apparatus for in-service flushing of solid particles, scale and debris from the working components of steam boiler low-water cutoff systems that connects to and employs the make-up water line.
What is further needed is a method and apparatus for in-service flushing of solid particles, scale and debris from the working components of steam boiler low-water cutoff systems that is simple in design.
What is further needed is a method and apparatus for in-service flushing of solid particles, scale and debris from the working components of steam boiler low-water cutoff systems that is inexpensive and simple to install.